The present invention relates to a refrigeration unit, and more particularly relates to a refrigeration unit with use of R32 (chemical formula: CH2F2) as a refrigerant alternative to R22 (chemical formula: CHCIF2) or with use of mixed refrigerants containing at least 70 weight percent R32.
Global environmental challenges relating to refrigeration units or air conditioners that perform a refrigerating cycle with use of refrigerants include (1) ozonosphere protection, (2) energy conservation, (3) measures against global warming (emission control of CO2 ant the like), and (4) recycling of resources.
In the global environmental challenges, particularly in view of the ozonosphere protection, R22 (HFC22) is high in ODP (Ozone Depletion Potential) so that it is not regarded as a preferable refrigerant. Accordingly, as prospective refrigerants alternative to R22, there are R410A (HFC32:HFC125=50:50 (weight ratio)) and R407C (HFC32:HFC125:HFC134a=23:25:52 (weight ratio)). Some refrigeration units for performing a refrigerating cycle with use of R410A or R407C have achieved the same COP (Coefficient of Performance) as R22, and have already been manufactured as products.
As for energy conservation, there has already been notified that designated air conditioners are required to improve COP by approx. 4% by the end of September, 2004 (Notification No. 190 of the Ministry of International Trade and Industry based on xe2x80x9cLaw concerning the Rational Use of Energyxe2x80x9d). Therefore, in view of energy conservation, it is necessary to use refrigerants having a large COP value.
In addition, demands for prevention of global warming is becoming harder. In the field of refrigeration units or air conditioners, an index to global warming called TEWI (Total Equivalent Warming Impact) is used to evaluate the refrigeration units and air conditioners. The TEWI is expressed as the sum of an impact of refrigerants released to the air (direct impact) and energy consumption of a unit (indirect impact). The direct impact includes GWP (Global Warming Potential), while the indirect impact includes a reciprocal of COP. Consequently, in order to prevent global warming, or equivalently, to decrease the value of TEWI, it is necessary to select refrigerants having a small GWP value and a large COP value.
The GWP values of R407C and R410A are 1980 and 2340, respectively, which are slightly larger than the GWP value 1900 of R22. Accordingly, R32 (HFC32) is expected as a prospective refrigerant having a small GWP value for prevention of global warming. R32 has the GWP value of 650, which is about one third of the GWP values 1900, 1980 and 2340 of R22, R407C and R410A, and therefore considered to be an extremely small value.
The COP values of R407C and R410A are approximately equal to the COP value of R22, whereas the COP value of R32 is not larger than that of R22. More particularly, although the refrigeration unit for performing a refrigerating cycle with use of R32 is theoretically expected a high COP value because of the characteristics of R32, any actual result that significantly exceeds the COP of R22 is not provided so far. Also, use of R32 brings about a phenomenon of higher pressure and higher discharge temperature compared to use of R22. In addition to that, there is a problem of difficulty in reaching a safety consensus because R32 has slight flammability. Because of this reason, the industrial society has not adopted R32 as an alternative refrigerant product.
Accordingly, it is an object of the present invention to provide an energy-saving refrigeration unit against global warming that is capable of achieving high COP (Coefficient of Performance) with use of R32 having a small GWP (Global Warming Potential) as a refrigerant.
The present invention is invented based on finding by an inventor of the present invention that a tendency for the COP of a refrigeration unit to change in response to an amount of a refrigerant (the total amount for filling a refrigerant circuit) is considerably different in types of refrigerants, especially between R32 and other refrigerants including R410A. More particularly, as shown in FIG. 1a, in the case of using, for example, R410A, there is a tendency that the COP gradually rises and saturates with increase of an amount of the refrigerant within the range shown in the drawing. On the contrary, in the case of using R32, there is a tendency that the COP marks a peak with change of an amount of the refrigerant, and then shows a sharp drop once an amount of the refrigerant is out of the range that gives the peak. Conventionally, the reason why use of R32 fails to provide high COP compared to use of R410A is because the refrigerants are used in the range that is relatively large in amount of the refrigerant (1200 g to 1300 g in the case shown in FIG. 1a). The notable point here is that a peak value of the COP in the case of using R32 with change in amount of the refrigerant is much higher than the COP in the case of using R410A with an optimum amount of the refrigerant (1300 g in the case of FIG. 1a). This indicates that use of R32 with an amount of the refrigerant set in an appropriate range enables achievement of high COP.
As described above, R32 has GWP much lower than that of conventional R22 and R410A (about one third). Further, adequate selection of an amount of the refrigerant enables R32 to obtain COP higher than that of R410A and R22. This makes TEWI (Total Equivalent Warming Impact) of R32 smaller than the TEWI of R22 and R410A, thereby proving superiority of R32 in global warming characteristics compared to R22 and R410A.
The present invention provides a refrigeration unit for performing a refrigerating cycle by circulating R32 as a refrigerant through a refrigerant circuit comprising a compressor, a condenser, expansion means, and an evaporator, wherein an amount of R32 for filling the refrigerant circuit is in a range of 120 g to 450 g per kW of refrigerating capacity.
As shown above, an amount of R32 for filling the refrigerant circuit being in the range of 120 g to 450 g per kW of refrigerating capacity implements high COP.
Herein, measuring method of refrigerating capacity (kW) shall conform to the regulations of Japan Industrial Standard (JIS) C9612.
It is noted that since an amount of R32 for filling is xe2x80x9cin the range of 120 g to 450 g per kW of refrigerating capacityxe2x80x9d, the total amount of R32 for filling the refrigerant circuit is, for example, 600 g to 2250 g if the refrigerating capacity is 5 kW.
The present invention also provides a refrigeration unit for performing a refrigerating cycle by circulating R32 as a refrigerant through a refrigerant circuit comprising a compressor, a condenser, expansion means, and an evaporator, wherein an amount of R32 for filling the refrigerant circuit is in a range of 400 g to 750 g per liter of unobstructed capacity of the condenser.
As shown above, an amount of R32 for filling the refrigerant circuit being in the range of 400 g to 750 g per liter unobstructed capacity of the condenser implements high COP.
It is noted that the reason why an amount of R32 for filling the refrigerant circuit is prescribed as xe2x80x9cper liter unobstructed capacity of the condenserxe2x80x9d is because the unobstructed capacity of the condenser is dominant over an amount of the filling refrigerant.
Also, since an amount of R32 for filling is xe2x80x9cin a range of 400 g to 750 g per liter of unobstructed capacity of the condenserxe2x80x9d, the total amount of R32 for filling the refrigerant circuit is, for example, in the range of 600 g to 1125 g if the unobstructed capacity of the condenser is 1.5 liter.
The principles of the invention are not only applicable to a single refrigerant of R32, but also applicable to mixed refrigerants containing at least 70 weight percent R32.
The present invention also provides a refrigeration unit for performing a refrigerating cycle by circulating mixed refrigerants containing at least 70 weight percent R32 through a refrigerant circuit comprising a compressor, a condenser, expansion means, and an evaporator, wherein an amount of the R32 for filling the refrigerant circuit is in a range of 84 g to 450 g per kW of refrigerating capacity.
In the case of using mixed refrigerants containing at least 70 weight percent R32 as shown above, an amount of R32 for filling the refrigerant circuit being in the range of 84 g to 450 g per kW of refrigerating capacity implements high COP.
The present invention also provides a refrigeration unit for performing a refrigerating cycle by circulating mixed refrigerants containing at least 70 weight percent R32 through a refrigerant circuit comprising a compressor, a condenser, expansion means, and an evaporator, wherein an amount of the R32 for filling the refrigerant circuit is in a range of 280 g to 750 g per liter of unobstructed capacity of the condenser.
In the case of using mixed refrigerants containing at least 70 weight percent R32 as shown above, an amount of R32 for filling the refrigerant circuit being in the range of 280 g to 750 g per liter of unobstructed capacity of the condenser implements high COP.